1. Field of the Invention
The present invention relates to liquid crystal display devices and a method for manufacturing the same. More particularly, the present invention relates to a liquid crystal display device (LCD) having thin film transistors arranged in a zigzag pattern at opposite sides of a gate line to prevent the occurrence of Cgd variation, even when gate lines or data lines are misaligned in the Y- or Z-axis direction, and a defective interface caused by stitching.
2. Background of the Related Art
In keeping pace with the developments of an information oriented society, the demands for display devices have gradually increased in various forms. To meet the demands, various flat display devices, such as Liquid Crystal Display (LCD), Plasma Display Panel (PDP), Electro Luminescent Display (ELD), and Vacuum Fluorescent Display (VFD), have been studied.
Of the various types of display devices, the LCD is used the most for mobile display devices because of its advantages, i.e., good picture quality, light weight, thinness, and low power consumption and has replaced the Cathode Ray Tube (CRT). Besides the mobile display devices, such as monitors for notebook computers, the LCD has been used as monitors for televisions to receive and display broadcast signal, and as monitors for computers.
The LCD device includes a liquid crystal panel for displaying a picture and a driving part for applying a driving signal to the liquid crystal panel. The liquid crystal panel is provided with opposite first and second glass substrates, and a liquid crystal layer between the first and second glass substrates.
The first glass substrate (also called a TFT array substrate) includes a plurality of gate lines arranged at regular intervals in one direction, a plurality of data lines arranged at regular intervals perpendicular to the gate lines, a plurality of pixel electrodes on sub-pixel regions defined by the gate lines and the data lines in a form of a matrix, and a plurality of thin film transistors that are to be switched in response to signals on the gate lines for transmission of signals on the data lines to the pixel electrodes.
On the second glass substrate (also called a color filter substrate), there are a black matrix layer for shielding a light to parts excluding the sub-pixel regions, R, G, B color filter layers for displaying colors, and a common electrode for displaying a picture. In an IPS type LCD, the common electrode is on the first glass substrate.
FIG. 1 illustrates a related art LCD circuit having a zigzag TFT arrangement, including a plurality of gate lines G1˜Gn, Gn+1, Gn+2 . . . , a plurality of common lines Vcom_odd, and Vcom_even parallel to and between the gate lines, a plurality of data lines D1˜Dm, Dm+1, Dm+1 . . . perpendicular to the gate lines, and TFTs arranged in a zigzag pattern at opposite sides of the gate lines, i.e., at an X-axis, each connected to the gate line, the data line, and the common line.
The thin film transistor TFT has a drain electrode ‘d’ connected to an adjacent pixel electrode ‘P’, a gate electrode ‘g’ connected to the gate line Gn, and a source electrode ‘s’ connected to the data line Dm. There are a capacitor having a liquid crystal capacitance Clc, and a capacitor having a storage capacitance Cst connected in parallel between the drain electrode ‘d’ and the common electrode. The liquid crystal capacitance Clc, and the storage capacitance Cst act as a load the TFT-LCD is required to drive. There can be parasitic capacitance Cgd caused by misalignment between the gate electrode ‘g’ and the drain electrode ‘d’.
In the TFT-LCD, after making the TFT conductive by applying a gate-on voltage to the gate line Gn connected to the gate electrode ‘g’ intended to display, a data voltage indicating a picture signal is applied to the source electrode ‘s’, to apply a data voltage to the drain electrode ‘d’. Accordingly, the data voltage is applied to capacitors of the liquid crystal capacitance Clc, and the storage capacitance Cst respectively, and a field is formed by a voltage difference of the pixel electrode and the common electrode Vcom.
FIG. 2 illustrates a plan view of the LCD in FIG. 1.
Referring to FIG. 2, the LCD is provided with a plurality of gate lines 11 arranged at regular intervals in one direction, and a plurality of data lines 13 perpendicular to the gate lines 11 at regular intervals, to define pixel regions on a transparent lower substrate (not shown). The gate lines 11 and the data lines 13 cross to define the pixel regions, and the thin film transistors TFT1, and TFT2 are formed on respective cross regions.
The thin film transistor has a gate electrode 1a projected from the gate line 11, a gate insulating film on an entire surface of the lower substrate inclusive of the gate electrode 11a, an active layer 12 on the gate insulating film over the gate electrode 11a, a source electrode 13a projected from the data line 13 in a ‘⊂’ form, and a drain electrode 13b between two forks of the source electrode 13a. 
There are a common line 11b and a plurality of common electrodes 11c on the same layer with the gate line 11, wherein the common line 11b crosses the pixel region parallel to the gate line 11, and the plurality of common electrodes 11c are arranged on the pixel region parallel to the data line 13. The common electrodes 11c are symmetric with reference to the common line 11b in an up/down direction and connected to each other.
There are a protection film (not shown) on an entire surface of the lower substrate inclusive of the data line 13 and a pixel electrode between the common electrodes 11c. The pixel electrodes 13c are also symmetric with reference to the common line 11b in an up/down direction. The pixel electrode 13c is connected to the drain electrode 13b to form a unit. There is a storage electrode 13d connected to the pixel electrode 13c on the common line 11b, to form a Storage On Common structure.
When the TFTs are arranged at opposite sides of the gate line in zigzag, if misalignment occurs in a Y-axis direction, resulting to change an overlap area of the gate electrode and the drain electrode of the TFT, a Cgd difference occurs between adjacent pixel regions.
Moreover, when the liquid crystal display device is applied to a large sized liquid crystal panel, if misalignment occurs at a shot interface region of the large sized liquid crystal panel fabricated in multi-shot, a potential problem of defective interface region coming from stitching due to the Cgd difference between the adjacent pixels.